1. Field of the Invention
The present invention relates to the field of electrical machines. It relates to a rotating electrical machine and to a method for producing such a machine.
2. Brief Description of the Related Art
Such machines are known, for example, from DE-A1-197 26 563 or DE-A1-102 15 937.
In large rotating electrical machines, such as turbogenerators, for example, in a power range of up to several 100 MW, the stator winding is constructed by winding bars having a rectangular cross section, which are inserted and wedged into axial slots provided for this purpose in the laminate stack. Two winding bars are often arranged one above the other in a lower layer and in an upper layer within the slots (see, for example, the aforementioned DE-A1-197 26 563). The winding bars of the lower layer and upper layer emerge from the stator body at both ends and are each connected to one another or to terminals for the stator winding in an end winding with a predetermined scheme so as to form the stator winding. For this purpose, the winding bars are bent outwards, outside the stator body, by a fixed angle such that they lie, with their end sections, on a cone about the machine axis. At the same time, the end sections are bent (twisted) on the cone casing transversely with respect to the axis in order to bring, in accordance with the scheme, a winding bar from the lower layer of one slot and a winding bar from the upper layer of another slot together at the ends such that they lie one above the other in pairs on concentric circles and can be connected directly to one another.
With selected pairs of bar ends, which belong to different phases of the stator winding, no connection is produced. Instead, the bar ends, which lie one above the other, are connected separately to terminals of the machine for the stator winding (see FIG. 3 in DE-A1-197 26 563). Since the full voltage may be present between the two bar ends of such a phase segregation pair, particular precautions need to be taken in order to ensure the required dielectric strength in this region. One of these precautions, which has been suggested and has proven successful in practice, consists in spreading the bar ends, which initially lie directly one above the other, of the upper layer and lower layer tangentially on the cone of the end winding, i.e., bending them laterally apart from one another in opposite directions.
However, this precaution has the following disadvantages: while all the winding bars of the upper and lower layers have the same “pitch” or twisting angle in the end winding without any tangential spreading, for each tangential spreading two winding bars with a different pitch need to be produced. In addition, it may be necessary for a different pitch to be provided for a winding bar pair which is adjacent to the phase segregation pair in order to provide space for the tangential spreading. In practice, this means considerable additional complexity when producing the winding bars.